The present invention relates generally to auxiliary hydraulic systems for skid steer loaders. In particular, the present invention is an electrically actuated and controlled auxiliary hydraulic system with cyclical operating mode selection.
Skid steer loaders are compact, highly maneuverable vehicles which are maneuvered by an operator seated within an operator compartment by actuating a pair of steering levers. The extent to which each lever is pushed in a particular direction controls the speed at which the wheels on that side of the vehicle will rotate. Similarly, the extent to which the lever is pulled in a reverse direction will control the speed at which the wheels on that side of the vehicle are rotated in a reverse direction.
Attachments such as an auger, a grapple, sweeper, landscape rake, snowblower or backhoe which include their own hydraulic motor are sometimes mounted to a boom assembly on the front of the skid steer loader. An auxiliary hydraulic system is used to control the flow of hydraulic fluid between the skid steer loader auxiliary hydraulic pump and the hydraulic motor on the front mounted attachment. Attachments such as scarfers or stabilizers which also include hydraulic motors are sometimes mounted to the rear of the loader. These rear mounted attachments are also supplied with hydraulic fluid from the auxiliary hydraulic pump by an auxiliary hydraulic system.
Electrically controlled auxiliary hydraulic systems have been used in conjunction with skid steer loaders. In one skid steer loader, the electrically controlled auxiliary hydraulic system includes electromechanic devices, including relays, to perform logic and switching operations. Electromechanical relays include a spring which holds an armature in a normal position and a coil which, when energized, positions the armature to make contact with a particular contactor. However, electromechanical relays are susceptible to mechanical shock and vibration, and are adversely affected by the rugged environment in which the skid steer loader normally operates. Therefore, a skid steer loader with an improved electrically controlled auxiliary hydraulic system is desired.